Spin Spray‐Deposited Nickel Manganite Thermistor Films For Microbolometer Applications

Abstract

Nickel manganite thin films are good candidates for thermal imaging applications because of their large temperature coefficient of resistance (TCR), (>−3%/K) and good environmental stability. To enable low‐temperature deposition (90°C) on preexisting circuitry, a spin spray technique was developed for these materials. As‐deposited manganese oxide films show well‐developed X‐ray diffraction patterns, while as‐deposited nickel manganite films exhibit a nanocrystalline spinel structure. Low‐temperature (400°C) postdeposition annealing leads to densification of the nanocrystalline nickel manganite spinel films. Spectroscopic ellipsometry measurements on annealed films provide complex dielectric function spectra over a range from 0.75 to 5.15 eV with comparable features with those found in films prepared by a chemical solution method. Energy‐dispersive X‐ray spectroscopy indicates that the final composition of the films is Ni deficient relative to the starting solution composition. The TCR of the nickel manganite films annealed at 400°C in an argon atmosphere is −3.6%/K. Doping the nickel manganite films with zinc results in an improvement of crystallinity, but leads to substantial increases in the electrical resistivity. Copper doping reduces the resistivity of the films to <1.0 kΩ·cm without degrading the crystalline quality, thus resulting in films suitable for microbolometer applications.

In-plane impedance spectroscopy in aerosol deposited NiMn2O4 negative temperature coefficient thermistor films

“…[12][13][14] Nevertheless, the pure NMO compound is still the subject of recent research efforts in order to establish new and more efficient synthesis routes [15][16][17][18][19][20][21] and thin and thick film production techniques. [22][23][24][25][26][27][28][29][30][31] Furthermore, the interplay between the physical properties and the Ni and Mn cation distribution on the tetrahedral and octahedral sublattices is still a matter of debate.…”

Correlation between electrical properties and cation distribution in [(Ni Mn1-)0.84Cu0.16]3O4 thin films prepared by metal-organic decomposition for microbolometer applications

“…In previous study, we have also fabricated [(Ni 0.2 Mn 0.8 ) 1-x Cu x ] 3 O 4 (0.25 ≤ x ≤ 0.40) thin films using the metal-organic decomposition (MOD) method, and demonstrated that the thin films have high absolute TCR values (>3%/K) and low resistivity (<50 Ω cm) [4]. Although the TCR and resistivity outcomes are sufficient, it is not easy to apply them for use in an uncooled microbolometer because the annealing temperature is too high (450°C T annealing temperature (≤400°C) for the direct integration onto a substrate having complementary metal-oxide-semiconductor (CMOS) read-out circuitry [9].…”

Low Temperature Crystallization of Metastable Nickel Manganite Spinel Thin Films

“…Consequently, it is of interest to explore lower temperature methods compatible with CMOS integration. Spin spray deposition was used to prepare nanocrystalline nickel manganite films, at temperatures of 90°C . Reports of the formation of metastable, cation‐deficient, cubic nickel manganite spinel powders between 200°C and 400°C are also of interest.…”

“…In Refs. , reducing atmospheres, in some cases associated with the decomposition of organic precursors, were used to limit Mn oxidation. Higher oxidation states favor the formation of the bixbyite (Mn 2 O 3 ) and ilmenite (NiMnO 3 ) phases that are thermodynamically stable in air .…”

“…Spin spray deposition was used to prepare nanocrystalline nickel manganite films, at temperatures of 90°C. 8 Reports of the formation of metastable, cation-deficient, cubic nickel manganite spinel powders between 200°C and 400°C 9,10 are also of interest. In Refs.…”